This invention relates to a two-cycle diesel engine and more particularly to an improved arrangement for operating a two-cycle diesel engine to improve performance and increase emission control.
The fuel efficiency of diesel engines is well known. Although being fuel efficient, diesel engines do present certain problems, particularly with exhaust emission control. Because of their inherent high efficiency, diesel engines tend to have a higher amount of nitrous oxides (NO.sub.x) in their exhaust gases. In addition, under certain running conditions, the existence of carbon, hydrocarbon or carbon monoxide in the exhaust can be a problem.
A further objection to diesel engines is the particular noise which they generate under some running conditions. Because of the fact that a diesel engine begins combustion by self ignition due to the high compression ratio, a diesel engine may, at times, provide a knocking noise which some individuals may find to be objectionable. In order to overcome these disadvantages, it has been proposed to provide an arrangement for varying the compression ratio of the engine. With such variable ratio systems, a higher compression ratio is employed at low speeds and low loads and a reduced compression ratio is permitted at higher speeds and loads so as to reduce or control the aforenoted objectionable characteristics. With a two-cycle, crankcase compression, diesel engine, this can be done by providing an exhaust port timing control wherein the opening of the exhaust port is delayed at light loads and mid-range and is advanced under high speed operation. This changing of the timing of the opening and closing of the exhaust port has been found to be quite effective in overcoming the aforenoted disadvantages. However, even with such an arrangement, it has been found in the transition period immediately prior to or during the change of timing that certain of these objectionable characteristics may be encountered.
It is, therefore, a principal object of this invention to provide an improved diesel engine.
It is a further object of this invention to provide an improved arrangement for reducing the temperature in the combustion chamber of a diesel engine under certain running conditions.
It is a further object of this invention to provide an improved arrangement for operating a diesel engine so as to reduce objectionable characteristics under all running conditions.
It is a further object of this invention to provide the aforenoted advantages in an two-cycle, crankcase compression, diesel engine.